The present disclosure relates to an optical wafer defect inspection system and associated methodologies. Optical wafer inspection methods can be roughly classified into two categories, bright-field methods and dark-field methods. Described herein is a dark-field method.
Optical detection of nano-defects on wafers is a very challenging issue. Researchers have been trying many different methods to increase a defect signal-to-noise ratio (SNR) and enhance throughput to make defects of a size less than 20 nm detectable on an inspection tool in a manufacturing setting. Those methods include using short wavelength light illumination, different polarization states, stronger light sources, different angle of incidences (AOI), the use of high-quality imaging subsystems, aperture shaping, the use of low noise sensors, and the like.
The foregoing “Background” description is for the purpose of generally presenting the context of the disclosure. Work of the inventor, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.